Transcript ANS LAST 2012 foundation medical

Autonomic Nervous System
The Autonomic Nervous
Assess Prof. Fawzia Al-Rouq
System
Department of Physiology
College of Medicine
King Saud University
LECTUR (1)
Functional Anatomy
&
Physiology of
Autonomic NS
INTRODUCTION
THE NERVOUS SYSTEM
•The nervous system monitors and controls almost every
organ / system through a series of positive and negative
feedback loops.
•The Central Nervous System (CNS): Includes the brain
and spinal cord.
•The Peripheral Nervous System (PNS): Formed by
neurons & their process present in all the regions of the
body.
•It consists of cranial nerves arises from the brain &
spinal nerves arising from the spinal cord.
•The peripheral NS is divided into
•Somatic Nervous system
•Autonomic nervous system
The Autonomic
Nervous System
OBJECTIVES
• Anatomy and physiology of
Autonomic Nervous System
• At the end of this lectutre (1)the
student should be able to:• -appreciate the anatomy of
symathetic& parasympathetic nervous
system.
• -explain physiological functions of
Symathetic &parasympathetic nerves
in head&neck,chest,abdomen and
pelvis
FUNCTIONAL
ANATOMY OF THE
AUTONOMIC
NERVOUS SYSTEM
The Autonomic
Nervous System
• ANS is the subdivision of the peripheral
nervous system that regulates body activities
that are generally not under conscious control
• Visceral motor innervates non-skeletal (nonsomatic) muscles
• Composed of a special group of neurons
serving:
–
–
–
–
Cardiac muscle (the heart)
Smooth muscle (walls of viscera and blood vessels)
Internal organs
Skin
10
Basic anatomical difference between
the motor pathways of the voluntary
somatic nervous system (to skeletal
muscles) and those of the autonomic
nervous system
Basic anatomical difference between the motor
pathways of the voluntary somatic nervous
system (to skeletal muscles) and those of the
autonomic nervous system
• Somatic division:
– Cell bodies of motor neurons reside in CNS (brain
or spinal cord)
– Their axons (sheathed in spinal nerves) extend all
the way to their skeletal muscles
• Autonomic system: chains of two motor
neurons
– 1st = preganglionic neuron (in brain or cord)
– 2nd = ganglionic neuron (cell body in ganglion
outside CNS)
– Slower because lightly or unmyelinated
12
• Axon of 1st (preganglionic) neuron leaves
CNS to synapse with the 2nd (ganglionic)
neuron
• Axon of 2nd (ganglionic) neuron extends to the
organ it serves
this dorsal
root ganglion
is sensory
13
Sympathetic
Innervation of Visceral Targets
• Short, lightly myelinated preganglionic neurons
• Long, unmyelinated postganglionic neurons
• Ganglia close to spinal cord
Spina
l
Parasympathetic
Innervation of Visceral Targets
• Ganglia close to or on target organs
• Preganglionic neurons - long
• Post ganglionic neurons - short
SYMPATHETIC & PARASYMPATHETIC
NERVOUS SYSTEM ORIGIN
Blue= Para symp; Red symp
Sympathetic - Origin
• Thoracolumbar lateral horns of the spinal
segments T1-L2.
• Nerve fibers originate between T1 & L2
Parasympathetic - Origin
Craniosacral Cell bodies of
the motor nuclei of the cranial
nerves III, VII, IX and X in
the brain stem
 Second, third and fourth [S2S4] sacral segments of the
spinal cord
• Nerve fibers emerge from
brain &
• sacrum cranio-sacral outflow
PARASYMPATHETIC NERVOUS SYSTEM
 The cranial nerves III, VII and IX affect the
pupil and salivary gland secretion
 Vagus nerve (X) carries fibres to the heart,
lungs, stomach, upper intestine and ureter
 The sacral fibres form pelvic plexuses which
innervate the distal colon, rectum, bladder and
reproductive organs.
PHYSIOLOGICAL
FUNCTIONS OF THE
AUTONOMIC NERVOUS
SYSTEM
SYMPATHETIC NERVOUS SYSTEM
FUNCTIONS
FEAR, FLIGHT OR FIGHT
 The sympathetic system enables the body to be
prepared for fear, flight or fight
 Sympathetic responses include an increase in
heart rate, blood pressure and cardiac output
 Diversion of blood flow from the skin and
splanchnic vessels to those supplying skeletal
muscle
 Increased pupil size, bronchiolar dilation,
contraction of sphincters and metabolic changes
such as the mobilisation of fat and glycogen.
FUNCTIONS OF SYMPATHETIC NERVOUS
SYSTEM
Bronchioles dilate, which allows for greater
alveolar oxygen exchange.
It increases heart rate and the contractility of
cardiac cells (myocytes), thereby providing a
mechanism for the enhanced blood flow to skeletal
muscles.
Sympathetic nerves dilate the pupil and relax
the lens, allowing more light to enter the eye.
PARASYMPATHETIC
FUNCTIONS
NERVOUS
SYSTEM
 The parasympathetic nervous system has "rest and
digest" activity.
 In physiological terms, the parasympathetic system is
concerned with conservation and restoration of energy, as
it causes a reduction in heart rate and blood pressure, and
facilitates digestion and absorption of nutrients, and
consequently the excretion of waste products
PHYSIOLOGICAL
FUNCTIONS OF THE
AUTONOMIC NERVOUS
SYSTEM
The Autonomic Nervous System
Structu
re
Sympathetic Stimulation Parasympathetic Stimulation
Iris (eye
Pupil dilation
muscle)
Pupil constriction
Salivary Saliva production
Glands reduced
Saliva production increased
Mucus production
Mucosa reduced
Mucus production increased
Oral/nasal
Heart
Heart rate and force
increased
Heart rate and force
decreased
Lung
Bronchial muscle
relaxed
Bronchial muscle contracted
The Autonomic Nervous System
Structure Sympathetic Stimulation
Parasympathetic Stimulation
Stomach
Peristalsis reduced
Gastric juice secreted; motility
increased
Small
Intes
Motility reduced
Digestion increased
Large
Intes
Motility reduced
Secretions and motility increased
Liver
Increased conversion of
glycogen to glucose
Kidney
Decreased urine secretion
Adrenal
medulla
Norepinephrine and
epinephrine secreted
Bladder
Wall relaxed
Sphincter closed
Increased urine secretion
Wall contracted
Sphincter relaxed
THE AUTONOMIC
NERVOUS SYSTEM
Subdivis Nerves
ion
Employed
Location of
Ganglia
Chemical
Messenger
General
Function
Sympath Thoracolum Alongside
etic
bar
vertebral
column
Norepineph Fight or
rine
flight
Parasym Craniosacral On or near
pathetic
an effector
organ
Acetylcholi Conservati
ne
on of body
energy
LECTUR (2)
MECHANISM OF ACTIONS
The neurotransmitters &
receptors of Autonomic NS
OBJECTIVES
OBJECTIVES
• At the end of this lecture (2)the
student should be able to:• describe neurotransmitters that can
release at pre and post ganglionic of
Autonomic NS.
• Describe Autonomic NS receptors.
ANS Neurotransmitters: Classified as either cholinergic or adrenergic
neurons based upon the neurotransmitter released
Adrenergic
Cholinergic
Sympathetic Neurotransmitters
• Preganglionic neurons -
• Cholinergic = ( release acetylcholine )
• Postganglionic neurons:
release norepinepherine at target organs ie. Adrenergic
– except sweat glands & bl vessels to skeletal muscles
Parasympathetic Neurotransmitters
• Pre & Postganglionic neurons release
acetylcholine = Cholinergic
Chemical or neural transmitter
• All preganglionic fibers release
acetylcholine (Ach).
• All parasympathetic postganglionic
release Ach.
• All sympathetic postganglionic release
noradrenalin except sweat glands & bl
vessels to skeletal muscles
Autonomic Nervous system Receptors
Sympathetic Adrenergic Receptors
Parasympathetic cholinergic Receptors
• Alpha (α) adrenergic receptors are found in :
Adrenergic Receptors are either Alpha or Beta
– Iris
– Blood vessels
– GIT
• Beta (β) adrenergic receptors can be beta one (β1) or
beta 2 (β1)  found in :
– Heart (β1)Bronchioles (β2)
– Skeletal muscle (β2)
– GIT (β2)
• Norepinephrine mainly excite α (and β to a lesser
extent)
• Epinephrine excites both α & β equally
Adrenergic receptors
blockers
• α blockers:
Prazosin (α 1)
Yohimbine (α 2)
• β blockers:
Propranolol (β1 & β2)
Atenolol (β 1)
Cholinergic Receptors
Are divided into • Cholinergic Receptors
(1) Nicotinic  found in all ganglia ( i.e., the synapses •
between pre- & postganglionic of both sympathetic &
parasympathetic divisions of the ANS
(2) Muscarinic  found on all effector cells innervated ( •
& stimulated ) by 
(1) postganglionic parasympathetic fibers , & •
(2) postganglionic cholinergic sympathetic nerves (blood •
vessels of skeletal muscles & sweet glands)
Drugs block cholinergic receptors:
Hexamethonium (block both types)
Atropine (block muscarinic receptors)